Stefano Chelli

Worldwide evidence of a unimodal relationship between productivity and plant species richness

Grassland diversity and ecosystem productivity The relationship between plant species diversity and ecosystem productivity is controversial. The debate concerns whether diversity peaks at intermediate levels of productivity—the so-called humped-back model—or whether there is no clear predictable relationship. Fraser et al. used a large, standardized, and geographically diverse sample of grasslands from six continents to confirm the validity and generality of the humped-back model. Their findings pave the way for a more mechanistic understanding of the factors controlling species diversity. Science, this issue p. 302 The humped-back model of plant species diversity is confirmed by a global grassland survey. The search for predictions of species diversity across environmental gradients has challenged ecologists for decades. The humped-back model (HBM) suggests that plant diversity peaks at intermediate productivity; at low productivity few species can tolerate the environmental stresses, and at high productivity a few highly competitive species dominate. Over time the HBM has become increasingly controversial, and recent studies claim to have refuted it. Here, by using data from coordinated surveys conducted throughout grasslands worldwide and comprising a wide range of site productivities, we provide evidence in support of the HBM pattern at both global and regional extents. The relationships described here provide a foundation for further research into the local, landscape, and historical factors that maintain biodiversity.

Patterns of Clonal Growth Modes Along a Chronosequence of Post-Coppice Forest Regeneration in Beech Forests of Central Italy

Forest coppicing leads to changes in composition of the herbaceous understory through soil disturbance and alteration of the light regime. While the role of seed dispersal traits at the start of succession after coppicing has been extensively studied, the role of persistence traits such as clonal growth and bud banks is not yet sufficiently understood. To gain better understanding of this role, we studied the patterns of clonal growth organs and related clonal traits of species in a series of coppiced beech forests of the Central Apennines (Marches region, Italy) in various stages of recovery after the last coppicing event. We conducted stratified random sampling and established a chronosequence of recovery stages based on stand age (reflecting the number of years since the last coppicing). The beech stands were classified into three age groups (Post-logged, Recovering, and Old-coppice stands) according to the characteristic stages of beech coppice dynamics. Clonal growth organs and the corresponding clonal traits of plants in the forest understory vegetation were assessed with the help of a CLO-PLA1 database. We found no significant change in the proportion of clonal species along the studied chronosequence. In contrast, most of the traits and about the half of the clonal growth organs showed correlation with stand age or preference for a certain habitat (i.e., stage of regeneration). Clonal and bud bank traits proved to play an important role in the persistence of species subjected to forest coppicing cycles in the studied area.

Adaptation of the Canadian Fire Weather Index to Mediterranean forests

The Canadian Fire Weather Index (FWI) is one of the most used tools to forecast forest fire hazard. In this paper, we propose an adaptation of the FWI to take into account the Mediterranean vegetation and climate, to improve FWI performances for areas with these characteristics. In particular, the FWI has been calibrated for two Mediterranean regions (Algarve, Portugal and Peloponnese, Greece) by fitting the experimental data, collected in the field, for the forest fuel moisture content, with the values expected by the application of the original Canadian FWI. Field data were collected during the 2010 and 2011 fire seasons. The satisfactory results obtained by the adaptation of parameters from the original FWI, in spite of the small sample areas and limited time of collection, allowed us to verify the usefulness of the method in describing the fuel moisture dynamics and obtaining indexes closer to the characteristics of the Mediterranean forests considered. The adapted FWI, if further tested and extended to other sample areas, may help in a more detailed and precise application of the FWI index by improving the daily forest fire hazard forecast, to become also a better support for the Civil Protection Agency of Mediterranean countries.

Unravelling mechanisms of short-term vegetation dynamics in complex coppice forest systems

The silvicultural management of coppicing has been very common in deciduous forests in many European countries. After decades of decline of this practice, socio-economic changes might induce a revival valuing the biomass as a resource. New insights in the ecological processes that regulate plant diversity are relevant for a sustainable forest management. While studies on long-term changes are available, the short-term dynamics of the coppice forest understorey has not yet been explored. In this context, it is interesting to evaluate the species compositional changes, including the processes of species turnover and species impoverishment (nestedness) and to investigate the role of plant functional traits. For this purpose, we resampled a chronosequence of complex coppice beech forests of the Central Apennines (Italy) monitoring the short-time species dynamics of five years (i.e. from 2006 to 2011) in three age classes, i.e. post-logged, recovering and old coppice stands (0–16, 17–31 and > 32 years, respectively). In contrast to our expectation, declining species richness appeared only in the recovering stands, while the landscape scale (between-stand) heterogeneity, except for post-logged and recovering stands in 2011, did not change over five years. Significant temporal nestedness was found in each stage of succession. However, the rate of species turnover and species impoverishment do not significantly differ among the three age classes, indicating their constant importance along the forest regeneration after disturbance. Only in the early stage of forest regeneration after coppicing, species compositional changes are reflected by functional changes with surviving understorey species having clonal regeneration traits. Our results suggest an overall landscape-scale stability (and sustainability) of this coppice forest system. We conclude with management indications, highlighting the importance of maintaining the traditional local approach (coppicing with standards in small 0.5–1.0 ha sized management units with a ca 30-year rotation cycle) where active coppice parcels are interspersed by abandoned stands.

Distinctive and Pleasant – Transformative Concepts in Landscape Ecology: Social Ecological Green Spaces (SEGS)

Landscape means an area, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors. Unfortunately, this definition hides different criticalities in relation to landscape analyses. In this perspective, landscape ecology should begin to consider ownership types, labour relations, and social perceptions of quality of life, moving towards a concept that can be defined as social ecological green spaces (SEGS). The need for a change fits well with the Adriatic City, which is characterized by a highly fragmented and heterogeneous landscape. First attempts of research show that people’s perception is strictly related to thermal conditions which are strictly related to elements capable of reducing outdoor temperature such as green areas and green canopies. Multidisciplinary approach will help to characterize what could be defined as SEGS, relating the aesthetic, health, and emotional components of the urban quality of life to the shape, distribution, and species composition of green areas.

European Grasslands Gradient and the Resilience to Extreme Climate Events: The SIGNAL Project in Italy

Extreme weather events, land use, and the presence of invasive species can act as pressures threatening biodiversity, resilience and ecosystem services. Particularly in the open cultural landscape, these pressures can suddenly drive ecosystems across tipping points and beyond thresholds of system integrity. Yet, biodiversity holds features for buffering against change. Potential stabilizing mechanisms include species richness, presence of key species such as legumes, and intraspecific diversity. These potential buffers can be promoted by conservation management and political decisions. On this basis, the results of the SIGNAL project and the related scientific based knowledge, will help to develop recommendations that could be used by International, national and local authorities, EU institutions, NGOs, for agriculture, landscape management and biodiversity conservation. Here we briefly describe the project and the Italian field experimental site.